The Reds will meet Real Betis, Arsenal and Manchester United in the 'States.
“I assume this, but the resistance of the teams we play is strong,” the Dutchman told Liverpoolfc.com.
“We are trying to implement the ideas and keep doing what we have done so well. Keeping the boys fit, that’s the first aim.
“Those things are the first aim and then with all the players coming back I think the quality will definitely go up a lot as well and these two things – training sessions and boys coming back in – will help us to play even better than we did (on Friday against Preston).”
He also said, “It’s only two weeks in so if it was that easy to bring and to implement all your ideas in two weeks, that would have been an ideal situation but it doesn’t work like this!
“Like I said, the ones who came in from the start, they are still fit now, they have had two weeks of training sessions and stayed fit during the game so are getting fitter and fitter.
“But yeah, there are definitely more than a few areas where we have to improve but that will come with more sessions and it will definitely come when all the boys are in.”